fix the __init__ of several C-classes (#13211)

stdlib/_json.pyi

@@ -1,5 +1,6 @@
 from collections.abc import Callable
 from typing import Any, final
+from typing_extensions import Self
 
 @final
 class make_encoder:
@@ -19,8 +20,8 @@ class make_encoder:
     def encoder(self) -> Callable[[str], str]: ...
     @property
     def item_separator(self) -> str: ...
-    def __init__(
-        self,
+    def __new__(
+        cls,
         markers: dict[int, Any] | None,
         default: Callable[[Any], Any],
         encoder: Callable[[str], str],
@@ -30,7 +31,7 @@ class make_encoder:
         sort_keys: bool,
         skipkeys: bool,
         allow_nan: bool,
-    ) -> None: ...
+    ) -> Self: ...
     def __call__(self, obj: object, _current_indent_level: int) -> Any: ...
 
 @final
@@ -42,7 +43,7 @@ class make_scanner:
     parse_float: Any
     strict: bool
     # TODO: 'context' needs the attrs above (ducktype), but not __call__.
-    def __init__(self, context: make_scanner) -> None: ...
+    def __new__(cls, context: make_scanner) -> Self: ...
     def __call__(self, string: str, index: int) -> tuple[Any, int]: ...
 
 def encode_basestring(s: str, /) -> str: ...